The use of perforate projection screens is well known in the prior art as shown and described in U.S. Pat. No. 2,366,761 issued to R O Walker, U.S. Pat. No. 3,992,841 issued to R Ward, Jr and U.S. Pat. No. 4,750,807 issued to G Chamayou dit Felix.
Perforate screens are particularly useful as spherical or geodesic dome shaped screens used in planetariums to permit the flow of heating and cooling air through the screen to the inside of the domed screen from the space between the screen and the exterior dome of the planetarium thereby assuring the proper ventilation and temperature is maintained inside the domed screen and the viewing area of the planetarium.
One of the problems encountered when using a perforate screen is that when lap joints are used to connect adjacent perforate panels of the screen, the holes in overlapping edges of the adjacent panels are not always in alignment with each other and the surface of the overlapped panel sometimes shows through the holes in the overlapping panel edge thereby creating a strip of greater reflectivity than the rest of the surfaces of the panels where the holes are not blocked by the surface of an overlapped panel, or by a supporting frame member or some other object in close proximity to the back of the panel.
The prior art devices have attempted to eliminate these areas of greater reflectivity by applying black paint or black tape to the surface of any overlapped panel edges or frame members which would show through the holes in the overlapping perforate panels.
It has been found however, that even when black paint or tape is used to cover the overlapped surfaces there is still sufficient reflectivity from the black surfaces that the overlapped surfaces showing through the holes still create strips or areas of higher reflectivity than the rest of the screen. These strips or areas show up as light strips or other shapes on the screen and thereby break the desired continuity of the screen and distract from the images being projected on the screen. The problem of uniform reflectivity of the screen surface has been solved by my prior U.S. Pat. No. 5,011,263 (C L Hopper) which discloses and claims the use of dark material having vertically extending fibers on any surface which is overlapped by perforate sheets forming the projection screen surface.
In addition to the problem of non-uniform reflectivity described above, when the perforate patents are overlapped at interconnecting seams, a shadow is formed at the edge of the overlapped to panel which is visible when viewing the screen. This is most noticeable on the horizontal seams of the screen. Attempts have been made to solve this problem by beveling the edge of the overlapping panel to reduce the shadow appearing on the edge as may be seen in U.S. Pat. No. 3,992,841 issued to R Ward Jr and my prior U.S. Pat. No. 5,011,263, however, it has been found that beveling the edge does not sufficiently eliminate the shadow and the seam can still be seen by viewers of the screen.